The present invention relates to a machine tool and a method for cutting machining of work pieces, and in particular for metal cutting machining of metallic work pieces.
DE 196 35 258 C1 discloses a prior art machine tool having a tool spindle which is arranged on a traveling column so that it can be moved in three spatial axes perpendicular to one another. The tool spindle points downwards with its tool. A work piece spindle is mounted pivotably in a bridge below the tool spindle, so that the work piece spindle can be brought both into a horizontal and into a vertical position. The work piece spindle is designed such that a work piece rod can be pushed forwards from the rear through the work piece spindle until the front end of the work piece rod projects out of the work piece spindle. The front end can then be machined by means of a tool arranged in the tool spindle. This known machine tool can be advantageously used for producing a variety of work pieces from the rod.
In order to machine that end of the work piece which is held in the work piece spindle (machining of what is known as the sixth side), DE 196 35 258 C1 proposes an additional gripping and pivoting unit which is arranged opposite of the work piece spindle. The gripping and pivoting unit can take over a partly machined work piece from the work piece spindle, so that the sixth side is accessible then. Such a machine tool allows machining of the work piece at all six sides, while the work piece has to be rearranged once only. This is advantageous because each re-arranging may impair the machining accuracy due positional tolerances. Moreover, each re-arrangement takes time, which affects productivity.
In order to exploit the advantages of the known machine tool as well as possible, it is necessary to machine the first five sides of the work piece as completely as possible before the work piece is rearranged for machining the sixth side. This may present difficulties in the case of complex work pieces, for example when burrs occur on already machined work piece sides due to the machining of the sixth side. In such instances, the work piece has to be re-arranged a second time, contrary to the original idea, or separate re-machining is required.